This will get you to an answer for your simple case, but can you expand on how you'll know which columns will need to be compared (B and C in this case) and what the initial range (A1:D5
in this case) will be? Then I can try to provide a more complete answer.
Sub setCondFormat()
Range("B3").Select
With Range("B3:H63")
.FormatConditions.Add Type:=xlExpression, Formula1:= _
"=IF($D3="""",FALSE,IF($F3>=$E3,TRUE,FALSE))"
With .FormatConditions(.FormatConditions.Count)
.SetFirstPriority
With .Interior
.PatternColorIndex = xlAutomatic
.Color = 5287936
.TintAndShade = 0
End With
End With
End With
End Sub
Note: this is tested in Excel 2010.
Edit: Updated code based on comments.